Matter Around Us Book Back Questions 9th Science Lesson 10
9th Science Lesson 10
10] Matter Around Us
Book Back Questions with Answer and Do You Know Box Content
Do You Know?
Not all things that we see or feel are matter. For example, sunlight, sound, force and energy neither occupy space nor have any mass. They are not matter.
Atom: The smallest unit of an element which may or may not have an independent existence, but always takes part in a chemical reaction is called atom.
Molecules: The smallest unit of a pure substance, which always exists independently and can retain physical and chemical properties of that substances is called a molecule.
Examples: Hydrogen molecule consists of two hydrogen atoms (H2). Water molecule consist of two hydrogen atoms (H2) and one oxygen atom (O).
In the modern periodic table there are 118 elements known to us, 92 of which are naturally occurring while the remaining 26 have been artificially created. But from these 118 elements, crores of compounds are formed some naturally occurring and some artificial. Isn’t that amazing?
LPG – Liquefied Petroleum Gas: It is highly inflammable hydrocarbon gas. It contains mixture of butane and propane gases. LPG, liquefied through pressurisation, is used for heating, cooking, auto fuel etc.
Compounds of phosphorous, nitrogen and potassium are used in fertilizers. Silicon compounds are of immense importance in the computer industry. Compounds of fluorine are used in our toothpastes as they strengthen our teeth.
Blood is not a pure substance. It is a mixture of various components such as platelets, red and white blood corpuscles and plasma.
The air freshners are used in toilets. The solid slowly sublimes and releases the pleasant smell in the toilet over a certain period of time. Moth ball, made of naphthalene are used to drive away moths and some other insects. These also sublime over time. Camphor, is a substance used in Indian household. It sublimes to give a pleasant smell and is sometimes used as a freshner.
Solvent extraction is an old practice done for years. It is the main process in perfume development and it is also used to obtain dyes from various sources.
The beam of light coming from headlights of vehicles is due to Tyndall effect. Blue colour of sky is also to Tyndall effect.
Have you seen colourful patches on a wet road? When oil drops in water on road, it floats over water and forms a colourful film. Find out why.
Choose the best answers:
1. The separation of denser particles from lighter particles done by rotation at high speed is called _____________
(a) Filtration
(b) Sedimentation
(c) Decantation
(d) Centrifugation
2. Among the following _______________ is a mixture.
(a) Common salt
(b) Juice
(c) Carbon dioxide
(d) Pure silver
3. When we mix drop of ink in water we get a ________________
(a) Heterogeneous mixture
(b) Compound
(c) Homogeneous mixture
(d) Suspension
4. ___________________ is essential to perform separation by solvent extraction method.
(a) Separating funnel
(b) Filter paper
(c) Centrifuge machine
(d) Sieve
5. ______________ has the same properties throughout the sample.
(a) Pure substance
(b) Mixture
(c) Colloid
(d) Suspension
State true or false. If false, correct the statement:
1. Oil and water are immiscible with each other.
2. A compound cannot be broken into simpler substances chemically.
3. Liquid – liquid colloids are called gel.
4. Buttermilk is an example of heterogeneous mixture.
5. Aspirin is composed of 60%, Carbon, 4.5% Hydrogen and 35.5% Oxygen by mass. Aspirin is a mixture.
Match the following:
1. Element – settles down on standing
2. Compound – impure substance
3. Colloid – made up of molecules
4. Suspension – pure substance
5. Mixture – made up of atoms
Fill in the blanks:
1. A _____________ mixture has no distinguishable boundary between its components.
2. An example of a substance that sublimes is ______________.
3. Alcohol can be separated from water by ____________.
4. In petroleum refining, the method of separation used is ________________.
5. Chromatography is based on the principle of ___________________.
Answers:
Choose the best answers:
1. centrifugation 2. Juice 3. Homogeneous Mixture 4. Separating funnel 5. Pure substance
State true or false. If false, correct the statement:
1.True
2.False
Correct answer: A compound can be broken into simpler substances chemically
3.False
Correct answer: Liquid – solid colloids are called gel.
4.True
5.False
Correct answer: The constituents of Aspirin are fixed ratio by mass. So it is a compound
Match the following:
1.Element- Made up of molecules
2.Compound- pure substance
3.Colloid- Settles down on standing
4.Suspension- Impure substance
5.Mixture- Made up of atoms
Fill in the blanks:
1. Homogenous 2. Naphthalene 3. Distillation 4. Fractional distillation